The present invention relates to locks, and more particularly to an improved cylinder assembly for a plate tumbler lock which includes a removable, self-retained, snap-in plate tumbler construction.
Conventional plate tumbler locks include a key operated cylinder rotatably mounted in a cylindrical sleeve. The cylinder includes a plurality of plate tumblers which are biased by springs to normally project into the sleeve to prevent rotation of the cylinder. When a properly bitted key is inserted into the key way of the cylinder, and thus through slots formed in each tumbler, the tumblers are retracted from the sleeve into their respective wards to unlock the cylinder and allow the cylinder to rotate within the sleeve.
In the manufacture, shipping and assembling of plate tumbler locks, the tumblers must be retained within the cylinder in order to prevent them from accidently falling out of the cylinder. The plate tumblers are spring loaded and, since each tumbler ward has an open top which opens to the external surface of the cylinder, there is nothing to prevent the springs from urging the plate tumblers from their wards when the cylinder is not contained within a lock housing such as a hollow cylinder sleeve. These cylinders typically are shipped separately from the remaining lock components, such as the sleeve, with the plate tumblers in place and thus the plate tumblers need to be held within the cylinder by some means. If, for example, an assembler accidentally permits one of these plate tumblers to pop out of the cylinder, there is a waste of time during assembly. If, however, two or more plate tumblers should accidentally fall out, the combination might be lost if these plate tumblers are not reinserted into the cylinder in the correct order.
In the past, plate tumblers have been held in place by means of a retaining plate placed over the open top of the tumbler access wards in the cylinder. This retaining plate is typically staked into the cylinder. Other methods of retaining the plate tumblers include tumblers that "snap into" the cylinder by forming a shoulder on the plate tumbler for engagement with a corresponding detent or other means on the cylinder housing. Examples of such retaining methods are shown in the following U.S. Pat. Nos.: 1,726,614; 1,860,708; 2,123,940; 2,890,582; 3,137,156; 4,416,129; 4,672,827.
It is also often desirable for security reasons to remove and replace the tumblers in order to change the keys which will operate the lock, such as for new tenants or employees. Unfortunately, most tumblers utilized in a snap-in construction are themselves not removable once assembled. Also, prior snap-in tumblers are force fit into their respective tumbler wards during assembly. This force fitting of the tumbler during assembly typically causes burrs or metal deformation of either the projecting detent on the tumbler or the retaining ledge in the ward or both resulting in the accuracy of the tumbler being compromised since the tumbler may not properly locate itself against the retaining ledge formed in the ward. Thus, a key may not properly cooperate with such a tumbler resulting in a defective lock.
One self-retained, snap-in tumbler is illustrated and described in U.S. Pat. No. 5,088,305. However, the tumbler described therein, although removable, may still result in deformation of the detent projecting from the tumbler or the retaining ledge on the tumbler ward since the detent must be forced to pass over the retaining ledge.
It would thus be desirable to provide a cylinder assembly having a self-retained snap-in plate tumbler which does not require force fitting of the tumbler during assembly, and which further may be easily removed for replacement when desired.